Biomedical subjects

T J Lawlor

Publications and source records attributed to T J Lawlor.

22 records · Page 2Linked to original sources

PubMed1991

Correlations among linear type traits and somatic cell counts.

Genetic and phenotypic correlations between linear type traits and SCC were estimated from lactation average SCC from Pennsylvania DHIA and Holstein linear type evaluations from Sire Power, Inc. and Holstein Association using REML. Correlations were estimated between linear type traits and SCC measured in first lactation and between linear type traits measured in first lactation and SCC measured in second or third lactation. Data sets ranged in size from 4294 daughters of 216 sires to 58,235 daughters of 301 sires. Phenotypic and genetic correlations between the linear traits that reflect body and locomotive characteristics and SCC were generally small and unimportant. Phenotypic correlations between udder traits and SCC were variable, but cows with higher udder depth scores (higher udders) had lower SCC. Genetic correlations between udder traits and SCC were also variable. Genetic correlations between SCC and udder depth, SCC and fore udder attachment, and SCC and teat placement were negative (favorable). Genetic correlations between teat length and SCC tended to be positive. Genetic correlations were largest in magnitude between udder depth and SCC and ranged from -.21 to -.64 (weighted mean = -.35). Selection for higher udders and closer teat placement will likely improve resistance to mastitis in dairy cattle.

Animals↗

PubMed1990

Prediction of transmitting abilities for Holstein type traits.

Heritabilities and genetic and phenotypic correlations among 14 linear type traits were estimated from Holstein Association data by multiple trait REML. Data used for parameter estimation were records of 779,391 daughters of 871 sires included in the January 1988 sire evaluation. Each daughter was represented by her appraisal closest to 30 mo of age. Highest heritability was .37 for stature, and lowest was .10 for foot angle. Gains in reliability from using correlated traits in multiple trait prediction were large for some traits (up to 60% for foot angle for cows). Final score variance parameters were estimated from 953,596 records, which were 43% of records included in the national sire evaluation. Sire models that adjusted or did not adjust for merit of mates were compared. Heritability of final score was .27 with adjustment for merit of mates by subtraction of predicted transmitting ability of dam from daughter's record compared with .29 if mate was ignored. Evaluations for type for several popular older sires were reduced moderately by adjustment for merit of mates, but estimated genetic trend increased slightly. An improved genetic grouping procedure that considers group effects as inherited was adapted for use in sire models. Parameter estimates and models presented were implemented by the Holstein Association for computing July 1988 genetic evaluations for linear traits and final score.

Analysis of Variance↗

PubMed1987

Genetic evaluation of dairy goat does for milk and fat as an extension of buck evaluation.

The current procedure for calculating genetic evaluations of dairy goat bucks provides easily accessible information for constructing genetic evaluations for dairy goat does (doe indexes). Relationships among sires are accounted for by using the additive genetic relationship matrix among sires if the doe's sire was evaluated. The sire evaluation plus a portion of residual doe effect is the basis of doe evaluation. Although direct incorporation of maternal relationships among does may be accomplished, it requires extensive computations for large data sets. An approximate procedure based on selection index principles includes information from a doe's dam with only a modest increase in computing expense over that for genetic evaluations of bucks. Doe indexes were computed and adjusted to separate breed bases. Trend in doe indexes was positive for all breeds and ranged from .54 to 1.37 kg/yr for milk yield and from .021 to .052 kg/yr for fat yield.

Animals↗

PubMed1984

Performance of crosses among Hereford, Angus and Simmental cattle with different levels of Simmental breeding. I. Preweaning growth and survival.

Performance through weaning of 543 calves raised on 3-yr-old and older Hereford dams was studied. Calf breed groups were straightbred Hereford, 50% Angus-50% Hereford, 25% Simmental-75% Hereford and 50% Simmental-50% Hereford. Breed group was a significant source of variation for gestation length, birth weight, calving difficulty, late survival (from 24 h to weaning), percentage of calves weaned per cow calving, 180-d weight, 180-d withers height and 180-d weight:height ratio. Breed group differences were not significant for early survival or weaning condition score and approached significance (P less than .10) for net kilograms weaned (zero if no calf was weaned and 180-d weight if a calf was weaned). Fifty percent Simmental calves had the heaviest birth weight (41.4 kg), most calving difficulty (1.19 score), heaviest 180-d weight (200.5 kg) and tallest 180-d height (101.3 cm). Fifty percent Simmental calves also had the longest gestation length (287.5 d), lowest late survival rate (95%) and largest weight:height ratio (2.00), although they did not differ significantly in the first two traits from 25% Simmentals and in the latter trait from 50% Angus. Herefords differed (P less than .05) from 50% Simmentals in all traits for which breed group was significant except for percentage of calves weaned. Fifty percent Angus and 25% Simmental calves were similar to Herefords for many traits.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Population Groups↗